import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while(true) {
            //1.读取请求并解析
            DatagramPacket requestPacker = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacker);
            String request = new String(requestPacker.getData(),0,requestPacker.getLength());
            //2.
            String response = process(request);
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0,response.getBytes().length,
                    requestPacker.getSocketAddress());
            //3
            socket.send(responsePacket);
            //4
            System.out.printf("[%s:%d] res: %s resp: %s\n",responsePacket.getAddress(),responsePacket.getPort(),
                       request,response);
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}






















//
//public class UdpEchoServer {
//    private DatagramSocket socket = null;
//
//    public UdpEchoServer(int port) throws SocketException {
//        socket = new DatagramSocket(port);
//    }
//
//    public void start() throws IOException {
//        System.out.println("服务器启动!");
//        while(true) {
//            //1.读取请求并解析
//            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
//            socket.receive(requestPacket);
//            //基于字节数组构造String
//            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
//            //2.根据请求计算响应
//            String response = process(request);
//            //把响应返回给客户端
//            //构造一个 DatagramPacket作为响应对象
//            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0,response.getBytes().length,
//                    requestPacket.getSocketAddress());
//            socket.send(responsePacket);
//
//            //打印日志
//            System.out.printf("[%s:%d] res: %s resp: %s\n",responsePacket.getAddress(),responsePacket.getPort(),
//                    request,response);
//        }
//    }
//
//    private String process(String request) {
//        return request;
//    }
//
//    public static void main(String[] args) throws IOException {
//        UdpEchoServer server = new UdpEchoServer(9090);
//        server.start();
//    }
//}
